Efficiency and productivity terms for water management: A matter of contextual relativism versus general absolutism

Growing water scarcity and increasing demands for agricultural products generate much debate about improving the agricultural sector's water use efficiency and productivity. Agricultural engineering traditions feed this debate with notions such as agricultural yield gaps and low water use efficiencies that draw attention to potential improvements. However, when perspectives are shifted from an irrigated field to a river basin, someone's (water) loss may be another's (water) gain. Such shifts in perspectives complicate the applications of our concepts of irrigation efficiency (IE), water use efficiency (WUE) and water productivity (WP). This paper studies the use and abuse of definitions and applications of concepts of IE, WUE and WP and examines their appropriate application for different scales and domains of water use. In this paper we argue that water management decisions are best informed by using IE and WP at the irrigation scheme and catchment level, respectively. This use can identify context specific opportunities and potentials for increased water use efficiency and productivity as well as the potential trade-offs in water re-allocations between diverse water users and uses.